Process for partial delignification and filling of a lignocellulosic material, and composite material structure able to be obtained by this process

Abstract

The invention relates to a process for treating a lignocellulosic material, preferably wood, comprising the following steps: (1) soaking of the material with organic fluid in order to dissolve at least 40% and at most 85%, in weight %, of the lignin of the material; (2) washing with organic fluid so as to discharge the dissolved lignin; (3) filling with a filling compound; and (4) finishing, so as to obtain a composite formed of a three-dimensional network of transformed filling compound incorporated into a cellulose and lignin network. The invention also relates to a composite structure able to be obtained in this way, and to any part comprising at least one such structure.

The invention claimed is: 
     
       1. A treatment process for treating a structure of lignocellulosic material, comprising:
 (a) soaking the structure of lignocellulosic material with at least one fluid to dissolve at least 40% and at most 85% by weight % of the lignin present in the material; 
 (b) washing the structure resulting from (a) with at least one fluid so as to discharge the dissolved lignin, so as to produce a partially delignified structure; 
 (c) filling the partially delignified structure with at least one filling compound, so as to produce a filled partially delignified structure; and 
 (d) finishing the filled partially delignified structure, so as to obtain a composite material structure formed of a three-dimensional network of transformed filling compound incorporated in a network of cellulose and lignin. 
 
     
     
       2. The treatment process according to  claim 1 , wherein the structure of lignocellulosic material is a trimming member, a finishing member or a structure member. 
     
     
       3. The treatment process according to  claim 1 , wherein the fluid used in (a) is:
 an aqueous solution comprising a mixture of sodium chloride and sodium hydroxide, or an aqueous liquid comprising monoethanolamine, or a basic solution comprising KOH; 
 an aqueous solution comprising a mixture of acetic acid and hydrogen peroxide, or an acidic solution comprising HBr, H 2 SO 4  or H 3 PO 4 ; 
 a fluid comprising at least one enzyme, possibly in the presence of at least one ionic liquid or in the presence of at least one ionic liquid and at least one cosolvent; 
 a pure ionic liquid; 
 an ionic liquid containing one or more enzymes in solution; 
 an ionic liquid in a mixture with at least one solvent miscible with the ionic liquid; 
 an ionic liquid in a mixture with at least one miscible solvent containing one or more enzymes in solution; 
 a biphasic system, of which one of the phases is constituted by an ionic liquid, pure or mixed with at least one miscible solvent, and the other phase is constituted by a supercritical fluid; 
 a biphasic system, of which one of the phases is constituted by an ionic liquid, pure or in a mixture with at least one miscible solvent, and the other phase is constituted by a supercritical fluid, furthermore containing one or more enzymes in solution in the phase containing the ionic liquid; or 
 any solution of a pure compound or of a mixture of compounds, containing at least one enzyme; and mixtures thereof. 
 
     
     
       4. The treatment process according to  claim 1 , wherein the soaking is preceded by a prior treatment step, comprising at least one sub-step of pre-soaking a structure of lignocellulosic material with at least one fluid; followed by at least one sub-step of pre-washing of the structure resulting from the pre-soaking sub-step, with at least one fluid, so as to discharge the dissolved compounds resulting from the sub-step of pre-soaking. 
     
     
       5. The treatment process according to  claim 1 , wherein the fluid used in (b) is ethanol, hexane, isopropanol, heptane or mixtures thereof. 
     
     
       6. The treatment process according to  claim 1 , wherein the filling compound is in the liquid state under the conditions of pressure and temperature of the filling, wherein the filling comprises soaking the partially delignified structure in a liquid co-polymer or polymer. 
     
     
       7. The treatment process according to  claim 1 , wherein the filling compound is a polymerizable monomer present in a monomeric solution at the conditions of pressure and temperature of the filling, the monomeric solution further comprising at least one catalyst. 
     
     
       8. The treatment process according to  claim 7 , wherein the monomeric solution comprises at least one monomer of:
 monomers produced from petroleum; or 
 bio-sourced monomers. 
 
     
     
       9. The treatment process according to  claim 1 , wherein the dissolved lignin recovered from the fluid of washing is used in a process of exploiting the lignin for the manufacture of a construction material or of a material used in aeronautics or of a packaging material or of a biofuel or of a pharmaceutical compound or of a chemical compound. 
     
     
       10. The treatment process according to  claim 1 , wherein the lignocellulosic material is softwood, and 50 to 85% by weight %, of the lignin present in the structure is dissolved during the soaking. 
     
     
       11. The treatment process according to  claim 10 , wherein the lignocellulosic material is softwood, and 50 to 75% by weight % of the lignin present in the structure is dissolved during the soaking. 
     
     
       12. The treatment process according to  claim 1 , wherein the lignocellulosic material is hardwood, and 40 to 60% by weight %, of the lignin present in the structure is dissolved during the soaking. 
     
     
       13. The treatment process according to  claim 1 , wherein the lignocellulosic material is wood. 
     
     
       14. The treatment process according to  claim 8 , wherein the monomers produced from petroleum are methacrylates, phthalates; nitriles; styrene and styrenic derivatives; vinyl compounds; ethylenic compounds; butadiene; or isoprene; and wherein the bio-sourced monomers are terpenes; glycerol and glycerol derivatives obtained after reaction with at least one of epichlorohydrin, isomers of propanediol and glycolic acid; derivatives of sugars; furfural derivatives; lactic and formic acid derivatives; monomers produced from castor oil; hydroxyalkanoic acids; bio-ethylene; bio-ethylene glycol; bio-propylene; bio-1,4-butanediol; lignin derivatives; or mixtures thereof. 
     
     
       15. The treatment process according to  claim 1 , wherein the lignocellulosic material is hardwood, and 40 to 55% by weight % of the lignin present in the structure is dissolved during the soaking. 
     
     
       16. The treatment process according to  claim 1 , wherein the fluid used in (a) comprises an oxidizing compound such as sodium chlorite, bleach, or sodium hypochlorite; the fluid used in (b) comprises caustic soda; and/or the filling compound is methyl methacrylate. 
     
     
       17. A composite material structure comprising lignin, hemicellulose, cellulose and at least one filling compound, said structure obtained by the treatment process according to  claim 1 , wherein the composite material structure forms a three-dimensional network of transformed filling compound incorporated in a structure of cellulose and lignin. 
     
     
       18. A material structure according to  claim 17 , wherein the structure is substantially translucent. 
     
     
       19. A material structure according to  claim 17 , wherein the structure is a trimming member, a finishing member or a structure member. 
     
     
       20. A part comprising at least one composite material structure according to  claim 17 , said part being an item of furniture or part of an item of furniture, a component of a building, a packaging component, an automotive part or an aeronautical part.